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New genus and species of Seirini (Collembola

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Zoosystema33(4).indb545ZOOSYSTEMA • 2011 • 33 (4) © Publications Scientifi ques du Muséum national d’Histoire naturelle, Paris. www.zoosystema.com
KEY WORDS Collembola,
new combinations.
Bellini B. C. & Zeppelini D. 2011. — New genus and species of Seirini (Collembola, Ento- mobryidae) from Caatinga Biome, Northeastern Brazil. Zoosystema 33 (4) : 545-555. DOI: 10.5252/z2011n4a6.
ABSTRACT A new genus and a new species of Seirini (Entomobryidae) are described. Th e new genus, Tyrannoseira n. gen., is represented by three Brazilian Seira-like species with a peculiar type of sexual dimorphism: the fi rst pair of legs of adult males bears several spine-like setae in distinct positions, the femur is enlarged and the tibiotarsus is slender. Th e combination of these morphological features produces clasping structures used during male-male interactions. Th e new genus is known only from Caatinga, a unique semi-arid biome exclusively present in Brazil. A new species, Tyrannoseira sex n. sp., is also described from São João do Cariri, Paraíba State. Seira raptora and S. bicolorcornuta, described from Caatinga, are also included in the newly described genus. An identifi cation key for the three species of the new genus is also given. Sexual dimorphism and aspects of the systematics of Seira are discussed.
Bruno Cavalcante BELLINI Centro de Biociências, Departamento de Botânica, Ecologia e Zoologia,
Laboratório de Ecologia e Conservação da Biodiversidade, Universidade Federal do Rio Grande do Norte,
Campus Natal, Natal, RN (Brazil) [email protected]
Douglas ZEPPELINI Laboratório de Sistemática de Collembola e Conservação,
Centro de Ciências Biológicas e Sociais Aplicada, Universidade Estadual da Paraíba Campus V, João Pessoa, PB (Brazil)
New genus and species of Seirini (Collembola, Entomobryidae) from Caatinga Biome, Northeastern Brazil
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Bellini B. C. & Zeppelini D.
RÉSUMÉ Un nouveau genre et une nouvelle espèce de Seirini (Collembola, Entomobryidae) du biome de Caatinga, nord-est du Brésil. Un nouveau genre et une nouvelle espèce de Seirini (Entomobryidae) sont décrits. Le nouveau genre, Tyrannoseira n. gen., est représenté par trois espèces brésiliennes proches du genre Seira avec un type particulier de dimorphisme sexuel : la première paire de pattes des mâles adultes porte plusieurs épines et des soies en positions distinctes, le fémur est élargi et le tibiotarse est mince. La combinaison de ces caractéristiques morphologiques produit des structures qui sont utilisées pendant les confrontations entre les mâles. Le nouveau genre est connu seulement de la caatinga, un biome semi-aride unique existant exclusivement au Brésil. Une nouvelle espèce, Tyrannoseira sex n. sp., est également décrite de São João do Cariri, état de Paraíba. Seira raptora et S. bicolorcornuta, décrites de la caatinga, sont aussi incluses dans le nouveau genre. Une clé d’identifi cation pour les trois espèces du nouveau genre est également donnée. Le dimorphisme sexuel et la systématique de Seira sont discutés.
MOTS CLÉS Collembola,
INTRODUCTION
Entomobryidae Schött, 1891 is the most diverse family of Collembola with approximately 1700 described species (Bellinger et al. 1996-2010; Soto- Adames 2008). Th e typical entomobryid has long appendages as most species are epiedaphic and the body is covered by scales or small multiciliated microsetae and some macrochaetae. Entomobryidae also have the fourth abdominal segment at least twice as long as the third at the mid-line, there are abdominal botriothrica complexes that include microsetae and fan-shaped scales, crenulate dens and short mucro with one or two well developed teeth (Christiansen & Bellinger 1980, 1998; Soto- Adames et al. 2008).
Entomobryidae is separated in two subfamilies: Orchesellinae Börner, 1906 and Entomobryinae Schött, 1891. Within Entomobryinae, there are four recognized tribes: Entomobryini Schött, 1891, Lepidocyrtini Wahlgren, 1906, Willowsini Yoshii & Suhardjono, 1989 and Seirini Yosii, 1961 (Soto- Adames et al. 2008). In some classifi cations, Seirini and Willowsini appear as subfamilies of Entomo- bryidae (Bellinger et al. 1996-2010).
Th e Seirini (or Seirinae) comprises eight valid genera: Acanthocyrtus Handschin, 1925; Epimetrura
Schött, 1925; Lepidocyrtoides Schött, 1917; Lepido- sinella Handschin, 1920; Lepidosira Schött, 1925; Seira Lubbock, 1870; Sinelloides Bonet, 1942 and Vietsira Yoshii, 1994 (Soto-Adames et al. 2008). Th e most striking morphological characteristic of Seirini is the presence of coarse ribs or denticles covering the scales, which are sometimes pointed (Soto-Adames et al. 2008). Approximately 70% of the species of Seirini are Seira species (more than 180 species) (Bellinger et al. 1996-2010).
In Brazil, the tribe Seirini is represented only by Lepidosira (two species) and Seira (25 species) (Abrantes et al. 2010; Bellini et al. 2010). Even though Seira is the largest genus of Collembola in the country, little is known about the true diver- sity of the Brazilian collembolan fauna. Most of the territory has not been well sampled and most biomes, like Pantanal (fl ood plains in the Central West Region), Cerrado (Brazilian Savanna), Pampa (grasslands in the South Region) and Caatinga (semi- arid landscapes in the Northeastern Region), were almost entirely neglected (Abrantes et al. 2010). As an example, only 10 species are, so far, known from Caatinga, seven of which are endemic (Bellini & Zeppelini 2009a).
Herein we describe a new genus of Seirini from Caatinga, Tyrannoseira n. gen., to group Seira-like spe-
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ZOOSYSTEMA • 2011 • 33 (4)
cies with a peculiar sexual dimorphism in Collembola. Th is condition plus the chaetotaxic features point out to a monophyletic lineage of Seirini. Furthermore, a new species from São João do Cariri, Paraíba State is described belonging to the new genus.
MATERIAL AND METHODS
Th e specimens were mounted into glass slides following the methodology described by Chris- tiansen & Bellinger (1980). Th e specimens were observed and their morphology was drawn using a BX-41 Olympus optical microscope bearing a drawing tube. Th e chaetotaxy schemes follow the system of Christiansen & Bellinger (2000) modifi ed from Jacquemart (1974). Th e type material of Tyrannoseira sex n. sp. (holotype and six paratypes) is deposited at the Museu Nacional, Universidade Federal do Rio de Janeiro (CM/MNRJ/UFRJ) and two paratypes (one male and one female) are deposited in the collection of the Muséum national d’Histoire naturelle, Paris (MNHN).
SYSTEMATICS
Tribe Seirini Yosii, 1961
Genus Tyrannoseira n. gen.
DIAGNOSIS. — Entomobryid habitus, with body covered by yellowish to brownish apically rounded scales. Eyes 8 + 8. Head chaetotaxy with M2 micro- or mesochaetae, S0-S3 always as macrochaetae, resulting in a cephalic region 4 with a total of 7 macrochaetae (Figs 1; 6). Femora of the fi rst pair of legs on males variably enlarged, bearing a variable number of short and strong spines, concentrated on a ventral projection of the femora (Figs 2; 4F). First pair of tibiotarsi curved on males, bearing a single row of long spine-like setae (Figs 2; 4G). Ungues with four inner teeth, two of them unpaired and two paired at the med-line of the structure. Unguiculi acuminate with weakly serrated edges. Tenent-hairs strong and capitate with slightly serrated edges. Absence of macrochaetae on the fi rst abdominal segment of adults (Figs 1; 6). Dens crenulate, mucro falcate, without dental or mucronal spines (Fig. 4J).
TYPE SPECIES. — Seira raptora Zeppelini & Bellini, 2006.
OTHER SPECIES OF THE GENUS. — Tyrannoseira bicolor- cornuta (Bellini, Pais & Zeppelini, 2009) n. comb., described as Seira bicolorcornuta; T. sex n. sp.
ETYMOLOGY. — From the Greek tyrannos: ruler, usurper. Seira refers to the clear relationship with the type genus of Seirini.
DISTRIBUTION. — Caatinga biome, Northeastern Brazil. Good’s biogeographic zone 27 (Good 1974).
HABITAT. — Th e three known species of Tyrannoseira n. gen. are restricted to Caatinga biome, a semi-arid region exclusively seen in Brazil inside or nearby a sub-region named “Planalto da Borborema”. Th is area is known by a rocky irregular and preeminent relief. Th e climate of the area is “As” following Koeppen’s system, which means an equatorial predominant climate and the precipitation with a clear “dry summer” annual season (Kottek et al. 2006).
FIG. 1. — Dorsal macrochaetae distribution of: A, Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb.; B, T. bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb.
A B
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Bellini B. C. & Zeppelini D.
FIG. 2. — Femur and tibiotarsus of the fi rst pair of legs of males of: A, Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb.; B, T. bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb. Scale bars: A, B, 10 μm.
A
B
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ZOOSYSTEMA • 2011 • 33 (4)
REMARKS
Tyrannoseira raptora n. comb. was originally in Seira and it fi ts the current diagnoses of the genus (Zeppelini & Bellini 2006). On the other hand the species, T. bicolorcornuta n. comb. and T. sex n. sp. are clearly part a of monophyletic lineage inside the genus, as they show a unique type of sexual dimorphism among the Entomobryidae. Other species of Seira, like S. domestica Nicolet, 1842, S. mantis Zeppelini & Bellini, 2006 and S. uwei Barra, 2010 also show sexual dimorphic legs (Gisin & Gama 1962; Zeppelini & Bellini 2006; Palacios-Vargas & Castaño Meneses 2009; Barra 2010), but the morphological condition seen in Tyrannoseira n. gen. is strikingly diff erent from that of S. domestica and related species, suggesting a convergent origin of similar sexual dimorphism in both taxa. Th e most remarkable diff erence is seen in male femora, being enlarged with short strong spines emerging from a single spot on the ventral side of each femur in Tyrannoseira n. gen. as opposed to normal-shaped femora with large spines in a single row in S. domestica group (see Zeppelini & Bellini 2006 and Barra 2010). Th e tibiotarsi also show
important diff erences. In Tyrannoseira n. gen., the tibiotarsi are clearly curved at the apex and there is only a single row of long spines (Zeppelini & Bellini 2006; Bellini et al. 2009). In the domestica group, there are several short spines inside three rows at the apex of the tibiotarsi, and the size of spines in the structure is signifi cantly smaller than in Tyrannoseira n. gen. (Gisin & Gama 1962; Zeppelini & Bellini 2006; Barra 2010). Despite the size and number of spines, these diff erences on the legs of both groups also point to a more important feature: many spines, which are originated from setae, are clearly not homologous in Tyrannoseira n. gen. and the domestica group. To support this theory, there are several important diff erences on the dorsal chaetotaxy of both groups. Th ere are obvious diff erences in the distribution of dorsal macrochaetae in all segments, but there is a pattern within each group, especially on the head (7 macrochaetae in Tyrannoseira n. gen. and 9 macrochaetae in the domestica group on cephalic region 4) and abdominal segment I (no macrochaetae in Tyrannoseira n. gen. and 6 + 6 macrochaetae in the domestica group). In fact, the constant morphology showed by the domestica group
A B
FIG. 3. — Males of Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb. fi ghting: A, males grabbing each other to strike with legs, antennae and furca; B, male grabbing an antenna of another male. Scale bars: A, B, 100 μm.
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Bellini B. C. & Zeppelini D.
TABLE 1. — General features of species of Tyrannoseira n. gen. and Seira Lubbock, 1870. Abbreviations: A-, minor apical; M+, larger medial; +, present; -, absent; ?, not clearly observed.
Species
1 - 1.923 4 M+, A- 7 + + -
T. bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb.
1 - 2.143 4 - 4 + + -
T. sex n. sp. 1 - 2.1 4 M+, A- 4 + + - S. domestica Nicolet, 1842 2 + 2.75-3.2 4 M+, A- 4 - - + S. mantis Zeppelini & Bellini, 2006 2 + 3.33 4 M+, A- 6 - - + S. uwei Barra, 2010 ? +- ? 4 M+, A- 4 - - + S. mirianae Arlé & Guimarães, 1981 1-2 - 1.5-2.2 2-3 - 2 - - - S. andensis Jacquemart, 1980 ? - 1.65 3 - 2? - - -
indicates that it is very likely that this set of species also forms a monophyletic lineage inside Seira.
Our preliminary studies showed that males of T. raptora n. comb. use the fi rst pair of legs, modi- fi ed into a clasping organ, to grab other males dur- ing intrasexual agonistic behavior, when they fi ght for feeding areas (Fig. 3). Th is behavior possibly increases access to females, while at the same time it limits the number of reproductive competitors. We expect the same behavior in other members of the new genus.
Our laboratory and fi eld observations showed many important features on the behavior of T. rap- tora n. comb. and Seira species that can explain the selection of modifi ed legs in males and the dual origin of this feature in the whole group. First, species of both genera and possibly most Seirini are very active during day time. Aggressive intraspecifi c behavior was observed in T. raptora n. comb., S. mirianae Arlé & Guimarães, 1981, S. mendoncea Bellini & Zeppelini, 2009, S. nigrans Arlé, 1960 and S. po- tiguara Bellini et al., 2010 (Bellini & Zeppelini, unpubl.). Th e females of T. raptora n. comb., which lacks the modifi ed legs, can also fi ght grabbing each other when they protect feeding areas. We didn’t
observe the behavior of males grabbing each other in species other than T. raptora n. comb., but the behavior of the females of this last species suggests it is very likely that it occurs in some Seira species. In these particular cases, any morphological modifi ca- tion which raises the effi ciency in the fi ghts, like the emergence of spines or modifi cations in the form of the structure to increase the effi ciency of grabbing, would be rapidly incorporated into the populations as the males bearing them have higher rates of suc- cess during the reproduction process. Th at would explain the convergent origins of the modifi ed legs in Tyrannoseira n. gen. and in the domestica group and makes possible the discovery of other groups among the Seirini with minor or major modifi ca- tions to increase the fi tness of the structure.
Th e combination of head chaetotaxy with meso- chaetae M2 as and macrochaetae S0 to S3, and the lack of macrochaetae on abdominal segment I is not exclusive to Tyrannoseira n. gen. Two other neotropical Seira species, S. mirianae and S. andensis Jacquemart, 1980 also have the same combination of characters (Christiansen & Bellinger 2000) shown in Table 1. Th e overall dorsal chaetotaxy of both species is similar to that in Tyrannoseira n. gen. spe-
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FIG. 4. — Tyrannoseira sex n. sp.: A, habitus; B, apical bulb of the 4th antennal segment; C, right eye patch; D, labial papillae; E, setae of the labial triangle; F, anterior femur of males; G, anterior tibiotarsus of the males; H, trochanteral organ; I, second foot complex; J, distal dens with mucro. Scale bars: A, 100 μm; B-J, 10 μm.
A
B
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Bellini B. C. & Zeppelini D.
cies. It is very likely that S. mirianae, a sympatric species to T. raptora n. comb., is closely related to Tyrannoseira n. gen. However, only a phylogenetic analysis of Seira and Tyrannoseira n. gen. could provide support to this hypothesis.
Seira comprises more than 180 described spe- cies, many of which are incompletely described. Th is makes it diffi cult to produce a rapid and clear comparison among the species. Th erefore, a phylo- genetic revision and subdivision of the genus into manageable taxonomic groups is urgent. Seira is divided into three subgenera (Afroseira Yosii, 1959, Lepidocyrtinus Börner, 1903 and Seira s.s.) (Yosii 1959), but they are not well accepted and rarely used in current taxonomic work (Christiansen &
Bellinger 2000; Barra 2004a, b; Negri et al. 2005; Zeppelini & Bellini 2006; Bellini & Zeppelini 2008a, b, 2009b; Soto-Adames et al. 2008; Bellini et al. 2009, 2010). Th e most remarkable problem with this subdivision is the large number of species retained in Seira s.s. Afroseira is represented by only one species, S. rowani Yosii, 1959, which lacks the distal pair of botriothrica on the fourth abdominal segment. Th is particular morphology is probably a pedomorphic character on Seirini, since the fi rst instar of some species (probably all) like S. dowlingi Wray, 1959 (Soto-Adames 2008) and T. raptora n. comb. lacks these botriothrica. Lepidocyrtinus is a group of frequently elongated body species of Seira with large blunt setae on the dens, and less than
FIG. 5. — Tyrannoseira sex n. sp., dorsal chaetotaxy of: A, second and B, third abdominal segments.
A
B
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ZOOSYSTEMA • 2011 • 33 (4)
10 fi tting species (Arlé 1959; Yosii 1959; Bellinger et al. 1996-2010; Christiansen & Bellinger 2000). In South America, three species of Lepidocyrtinus were described by Arlé (1959) as Ctenocyrtinus, a genus posteriorly synonymized with Seira by Chris- tiansen & Bellinger (2000). While Afroseira and probably Lepidocyrtinus are monophyletic groups, they are not helpful in making easier the identifi ca- tion of many Seira species. Th e small monophyletic groups represented by Afroseira, Lepidocyrtinus and Tyrannoseira n. gen., leaves a paraphyletic Seira s.s. and a phylogenetic analysis of the whole group is needed to shade some light in the relationship in Seirini and test the monophyly of Seira s.s.
Tyrannoseira sex n. sp. (Figs 4-6)
TYPE MATERIAL. — Brazil. Paraíba, São João do Cariri, Furna dos Ossos, 15-16.VI.2008, Farias, A.A. Coll, holotype , 6 paratypes (5 , 1 ) (2175, CM/MNRJ); 2 paratypes (1 , 1 ) (EA010032, MNHN).
ETYMOLOGY. — Th e species was named after its sexual dimorphism.
DISTRIBUTION. — Good’s biogeographic zone 27 (Good 1974).
HABITAT. — Tyrannoseira sex n. sp. was collected in São João do Cariri municipality, about 200 km from João Pessoa, capital of Paraíba State, northeatern Brazil. Th e collections were made during the wet season (June 2008) inside an archeological site named “Furna dos Ossos”. Th e climate of the area is “As” following Koeppen’s system (Kottek et al. 2006) and the fl ora is hiperxerophytic with areas of typical Caatinga forest.
DESCRIPTION
Total length of the holotype 1.58 mm. Habitus typically entomobryid (Fig. 4A). Color of mounted specimens pale yellow, with light blue pigment cover- ing the antennae and dark blue pigment covering eyepatches and labrum area (Fig. 4A). Yellowish to brownish rounded scales covering head, thorax, abdomen, legs, antennal segments I and II, and basal halves of antennal segments III and IV. Ventral tube without scales. Fourth antennal segment not annulated, with a single apical bulb, without pin setae (Fig. 4B). Eyepatches oval, 8 + 8 lenses, biggest
lens B and smallest lens G, two interocular feathered mesochaetae and two interocular macrochaetae (Fig. 4C). Pre-labral and labral setae feathered. Labral papillae as show in Figure 4D. Labial triangle seta r reduced M1, M2 and E feathered (Fig. 4E). Femur of the fi rst pair of legs heavily broadened in males, bearing 10 strong spines (Fig. 4F). Male tibiotarsus of fi rst pair of legs apically slender with one row of 10 elongated spine-like setae (Fig. 4G). Trochanteral organ V- shaped with approximately 23 short spine-like setae (Fig. 4H). All ungues with four inner teeth, one pair at the base and two distal
FIG. 6. — Dorsal macrochaetae distribution of Tyrannoseira sex n. sp.
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Bellini B. C. & Zeppelini D.
unpaired teeth (Fig. 4I). Unguiculi acuminate, with slightly serrated edges (Figs 4I). Tenent hair capitate, slightly serrated at the edges. Venter of manubrium with 4 + 4 subapical multiciliated setae on a transversal line. No spine-like setae present on…